A conventional clock generator circuit used in the personal computer system have been designed so that the slaves such as I/O, CRT, memory and the like have been designed to become optimal relative to its clock because while the central processing unit (CPU) as a master is operating (running the cycle) the clock frequency and the duty ratio are constant in the entire computer system.
However, if the optimum design of the slaves is impossible, the conventional clock generator has a drawback that the performance of the personal computer system is degraded. Because the clock generator has to standardize to supply the latest clock signal for operating well the whole computer system having a lot of the slave units. Further, it also has a problem that if the clock standard is changed the slaves designed according to the clock standard used prior to the change cannot be used.